There is no way to add PSSCriptInfo block into existing script

[peetrike]

Summary of the new feature / enhancement

New-PSScriptFileInfo overwrites script contents, if there is any.
Update-PSScriptFileInfo refuses to do anything if PSSCriptInfo block is missing or doesn't contain Version, GUID and Author properties

Proposed technical implementation details (optional)

There should be a way to add PSSCriptInfo block to existing scripts, other than copying it from another script.